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Re: [Qemu-devel] [PATCH v2 for-2.5] virtio-pci: Set the QEMU_PCI_CAP_EXP


From: Marcel Apfelbaum
Subject: Re: [Qemu-devel] [PATCH v2 for-2.5] virtio-pci: Set the QEMU_PCI_CAP_EXPRESS capability early in its DeviceClass realize method
Date: Wed, 2 Dec 2015 19:21:20 +0200
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.1.0

On 12/02/2015 07:19 PM, Michael S. Tsirkin wrote:
On Wed, Dec 02, 2015 at 07:12:47PM +0200, Shmulik Ladkani wrote:
Hi Michael,

On Wed, 2 Dec 2015 18:49:24 +0200 "Michael S. Tsirkin" <address@hidden> wrote:
On Wed, Dec 02, 2015 at 05:11:28PM +0200, Marcel Apfelbaum wrote:
The only thing I want to mention here, (see earlier discussion: 
https://www.mail-archive.com/address@hidden/msg338963.html)
is that in some cases the PCI config space will have PCIe length, even if the 
device is not express.

To be more precise, the only interesting scenario is when we plug a virtio 
device directly into
the root complex, in this case we'll have a PCI device with a PCIe config space.

However this happens for other devices as well, it looks like a common practice.

Problem is, if this happens migration breaks as we
changed config space size from 2.4.

Correct me if wrong, but as long as a pre 2.5 hardware is used, Marcel's
x-disable-pcie gets on (see HW_COMPAT_2_4), thus the device will not be
a "pci_is_express", and it will have a small config space size. Isn't it
so?

Regards,
Shmulik

OK. Still, I do not want to migrate 4k of config space
for pci devices.


Shmulik, will you resend the patch with this minor change, or you prefer me to 
do it? 2.5 closes soon.

Thanks,
Marcel



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